The extraordinary scope of the archive held by the Britten–Pears Foundation, with its cache of something like 750 pieces of juvenilia, along with what amounts to at least 95 per cent of the manuscripts of mature works, including many which were withdrawn or unfinished or have been published posthumously, must be unique for any composer. It is a special privilege to have access to so much material, but it brings with it responsibilities, as well as a number of moral questions. Just as biographers are often taken to task for burrowing too deeply into the minutiae of an artist's life, and thereby perhaps missing the bigger picture, or misinterpreting the life, so musicologists may be tempted by this extraordinary abundance of new information – especially about the composer's early development – to place undue weight on it, or exaggerate its importance. In addition, because music is not directly accessible in the way that words (or pictures) are, there is the vexed question of whether or not works that the composer might have suppressed should see the light of day in terms of performance, or publication. Since we have many hundreds of unperformed works in the archive (most, but by no means all, consisting of juvenilia) this is an important question for us. It is an issue which we need to consider in several different ways.

When a lost manuscript of a composer of several centuries ago resurfaces, no one is likely to dispute whether or not the music should be performed, even if it adds little or nothing to our understanding of the composer. But we start to feel uneasy when missing or incomplete works are reconstructed – Bach's St Mark or St Luke Passions, for instance, or Mozart's Zaide, or Schubert's five unfinished piano sonatas, or his and Beethoven's more tenuous Tenth Symphonies.

The most significant unfinished piece to have fully entered the repertoire is, of course, Mozart's Requiem. There can be very few, if any, who would maintain that it should not be performed at all, as not representative of Mozart's final wishes, but of course there has been controversy for over 200 years about Süssmayr's contribution as regards both its extent and its competence; and as scholarship has become more focused, different versions have emerged, although none has completely won the day and supplanted the standard editions.